Work machines, such as those in the agricultural, construction and forestry industries, perform a variety of operations. In some instances, the machines are provided with a work implement or tool to perform a desired function. The work implement or tool, such as a bucket, forklift, or grapple, is movably coupled to a frame of the machine by a mechanical lift arm or boom. The lift arm or boom is operably controlled by a machine operator using controls disposed in a cab of the machine.
In one instance, the machine may have a bucket operably connected to a boom which is rotatably coupled to a frame of the machine. In another instance, a boom is connected to the frame with two or more links. The operator of the machine adjusts the position of the boom as well as the position of the bucket to collect a material which can be located at a ground level or at other heights above ground level. Once the material is collected in the bucket, the material is moved to a desired location which can be at the ground level or at the other heights above ground level. The operator, in different embodiments of the work machine operably controls the bucket height and the bucket angle using one or more joysticks. In one embodiment, a boom joystick adjusts both a velocity and height of the boom and a bucket joystick adjusts both a velocity and level of the bucket.
Even though the operator provides commands with the boom joystick and the bucket joystick, known work vehicles include a control system which maintains the bucket level with respect to ground using one or more sensors which can include boom angle or position sensors and bucket angle or position sensors. Such systems incorporate what is known as a closed loop control system where the sensed position and velocity are transmitted to a controller and used to modify the commands provided by the operator through the joysticks.
Such systems are quite complex, however, due the presence of a large number of sensors which not only require maintenance but also require calibration. What is needed therefore is a work machine that maintains relatively the same level of performance, while reducing not only the number of sensors, but reducing the level of complexity of the control system maintaining bucket location and position.